Method and apparatus for level ride lift

ABSTRACT

A lift having a platform with a substantially level ride is described. The lift also reduces the distance between the ground and the platform in the ground position. An extension plate having receiving portions for accommodating portions of the lift when the platform is in a bed level position.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending U.S. patent applicationSer. No. 11/100,805 filed on Apr. 6, 2005, the entire contents of whichis incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention relates generally to load lifting and loweringdevices and, more particularly, to a lift having a platform which isable to rest on or near the ground and remain substantially level duringraising and lowering.

2. State of the Art

A common type of load elevator or lift comprises a substantiallyrectangular platform connected at one edge to the swingable ends of alaterally spaced apart pair of linkage systems. The other ends of thelinkage systems are pivotally connected to a support such as the chassisof a vehicle or a loading dock. A power means, usually hydraulic, isinterconnected to the pair of linkage systems for moving the platformbetween ground level and that of the truck or dock or the like. Each ofthe linkage systems comprises first and second lateral links in the formof an upper arm and a lower arm. The swingable ends of the linkagesystems comprise a first vertical link between the upper and lower armsin the form of a shackle against which the weight of the platform andthe load thereon are imposed. The other ends of the linkage systemscomprise a second vertical link between the upper and lower arms in theform of the support to which the linkage systems are pivotallyconnected. In this manner, the upper and lower arms, the shackle and thesupport define a substantially parallelogram-shaped arrangement for eachof the linkage systems.

A problem typically encountered with the above-described linkage systemsis that they do not maintain a perfect parallelogram arrangement whenmoving the platform between a raised and lowered position. Rather, thefirst vertical link is slightly rotated during translation such that theplatform describes an arc as it is being raised or lowered. When locatedat or near ground level, this causes the outer edge of the platform tobe tilted or ramped towards the ground. This may not be suitable forsome loads, such as those resting on wheels or other mechanisms allowingfor lateral load movement.

One approach to addressing this problem has been to lower the platform afirst distance wherein the linkage systems are maintained in theparallelogram arrangement, i.e. without substantially rotating the firstvertical link, and then using additional mechanisms to move the platforma second distance into contact with the ground. This two-steptranslation method enables the platform to have a substantially levelorientation through most of its lifting range, but requires a complexlift assembly that is more difficult to manufacture and maintain.Moreover, the platform may still have to be slightly tilted whentranslating through the second distance in order to reach the ground.

What is needed is a lift that has a platform with a substantially levelride through its entire lifting range and that does not require the useof complex mechanisms for lowering the platform to a location on or nearthe ground.

BRIEF SUMMARY OF THE INVENTION

The present invention overcomes the above-described problems with priorart lifts by providing a method and apparatus for a lift with a platformwhich is able to rest on or near the ground and remain substantiallylevel during raising and lowering. The present invention accomplishesthis by use of a novel linkage system arrangement having an upper armand a lower arm coupled between a support frame and a shackle. Theshackle is attached to a platform support that holds a lift platform ina level position while touching or very nearly touching the ground.

In one embodiment according to the present invention, an actuator ispositioned above the upper arm and the lower arm of the linkage system,and the lower arm has sides forming a hollow configuration forsurrounding the lower arm and attaching to the actuator. Alternatively,the actuator may be positioned below, between or to the side of theupper arm and the lower arm.

In another embodiment according to the present invention, an activeopener arm is connected to the linkage system and assists in stowing andunstowing the lift platform.

In yet another embodiment according to the present invention, anextension plate cooperates with the lift platform for loading andunloading. The extension plate may have hinged sections, and may alsohave a removable center section for receiving locking rods.

Other and further features and advantages will be apparent from thefollowing detailed description of the present invention when read inconjunction with the accompanying drawings. It should be understood thatthe embodiments described are provided for illustrative and exemplarypurposes only, and that variations to, and combinations of, the severalelements and features thereof are contemplated as being within the scopeof the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, which illustrate what is currently considered to be thebest mode for carrying out the invention:

FIGS. 1A-1C show a prior art lift which tilts or ramps the outboard edgeof the platform to the ground.

FIGS. 2A-2B show one embodiment of a lift in accordance with the presentinvention.

FIGS. 3A-3F show multiple views of one embodiment of a lift inaccordance with the present invention with the platform in a fullystowed, partially stowed, partially unfolded, fully unfolded, and bedlevel positions.

FIGS. 4A-4B show one embodiment of an upper arm and a lower arm inaccordance with the present invention.

FIG. 4C shows one embodiment of an upper arm and a lower arm inaccordance with the present invention.

FIGS. 5A-5D show one embodiment of a shackle and platform support inaccordance with the present invention.

FIGS. 6A-6D show embodiments of extension plates in accordance with thepresent invention.

FIGS. 7A-7B show one embodiment of an underride in accordance with thepresent invention.

FIGS. 8A-8B shows one embodiment of how a lift in accordance with thepresent invention may be shipped and installed.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A and 1B show a prior art lift 10 which tilts or ramps itsplatform 34 to the ground. Lift 10 includes an upper arm 60 and asegmented lower arm 62. One end of upper arm 60 is rotatably coupled toa main frame 12 by a first upper pin 70, while the swingable end ofupper arm 60 is coupled to a shackle 74 by a second upper pin 72. Thesegmented lower arm 62 includes a member 80 rotatably coupled to a plateassembly 96. Member 80 is rotatably coupled to main frame 12 by a firstlower pin 94, and plate assembly 96 is coupled to shackle 74 by a secondlower pin 98. Lift 10 also includes a cylinder 40 coupled to main frame12 and to the inside of plate assembly 96. Platform 34 is rotatablycoupled to shackle 74 by second upper pin 72 and includes a supportmember 78 which rests against shackle 74 to support platform 34 frombelow.

FIG. 1B shows a side view of lift 10 in a lowered position. In thisposition, plate assembly 96 and/or shackle 74 contacts the ground, andplatform 34 is still substantially level. Platform 34 is supported frombelow by support member 78, which is in contact with the outboard faceof shackle 74. Cylinder 40 is then made to become shorter, causingmember 80 and plate assembly 96 to rotate with respect to each other and“break” and draw in lower pin 98 of shackle 74. This has the effect oftilting shackle 74 and thus platform 34. FIG. 1C shows a side view oflift 10 with platform 34 in a tilted or ramped position, after cylinder40 has been made to become shorter. As can be seen in FIGS. 1A-1C,platform 34 cannot be maintained in a level orientation while contactingthe ground.

FIGS. 2A-2B show one embodiment of a lift 100 in accordance with thepresent invention, in assembled and partially exploded views. Lift 100includes an upper arm 110 and a lower arm 120. Upper arm 110 isrotatably coupled to a frame 130 by a first upper pin 136, while theswingable end of upper arm 110 is coupled to a shackle 140 by a secondupper pin 142. Lower arm 120 is coupled to frame 130 by a first lowerpin 138 and to shackle 140 by a second lower pin 144. The points whereupper arm 110 and lower arm 120 couple to frame 130 and shackle 140 maysubstantially form a linkage system defining the sides of aparallelogram. Lift 100 also includes an actuator 150, for example ahydraulic cylinder, coupled to frame 130 and lower arm 120.

Lift 100 includes a platform support 170. Platform support 170 ispositioned adjacent to shackle 140 and rotatably fixed with respect tothe swingable end of lower arm 120 by second lower pin 144. A platform160 is coupled to and rests on platform support 170. FIGS. 2A-2B showthat an extension plate 200 may be installed to cooperate platformsupport 170 of lift 100, as described in further detail with respect toFIGS. 6A-6D, and lift 100 may also include an underride 190, describedin further detail with respect to FIGS. 7A-7B. Steps (not shown) mayalso be attached to underride 190, extension plate 200, or other partsof lift 100, as known in the art.

FIGS. 3A-3F show side views of lift 100 in various stages of moving froma raised to a lowered position. FIG. 3A shows lift 100 in a fully stowedstage, with upper arm 110 and lower arm 120 in a raised position. FIG.3B shows lift 100 in a partially stowed stage, with upper arm 110 andlower arm 120 in a lowered position. Shackle 140 contacts the ground oris very close to the ground. Platform 160 is forced partially outwardfrom the stowed position by an active opener arm 125, which assists inthe stowing and unstowing of platform 160, as described in furtherdetail with respect to FIGS. 5C-5D. FIG. 3C shows lift 100 with platform160 being partially unfolded. FIG. 3D shows lift 100 with platform 160being further unfolded. FIG. 3E shows lift 100 in the ground position,with platform 160 fully unfolded. Platform support 170 and/or shackle140 contacts the ground. Platform 160 is substantially level, and istouching or very nearly touching the ground. FIG. 3F shows lift 100subsequently raised with platform 160 at the vehicle bed or loading docklevel position.

FIGS. 4A-4B show one embodiment of upper arm 110 and lower arm 120 inaccordance with the present invention. Actuator 150 is positioned aboveboth upper arm 110 and lower arm 120 and is coupled to frame 130 andlower arm 120. In the illustrated embodiment, lower arm 120 has a hollowconfiguration which at least partially encloses or envelopes upper arm110 and allows actuator 150 to be coupled to the sides of lower arm 120.FIG. 4A also shows that lower arm 120 may include a channel which allowsan extension 123 to be coupled to upper arm 110 and to pass through thechannel for coupling to active opener arm 125.

In an alternative embodiment, lower arm 120 may not have continuoussides forming a hollow configuration, but may instead have discreteextensions which reach around upper arm 110 and allow actuator 150 to becoupled to lower arm 120. While not a requirement of the presentinvention, FIGS. 4A-4B show that actuator 150 is preferably positionedin substantially the same vertical plane as upper arm 110 and lower arm120. Configuring upper arm 110, lower arm 120, and actuator 150 torotate in substantially the same vertical plane reduces binding duringoperation. FIG. 4C shows actuator 150 rotating in a vertical planedifferent than a vertical plane of upper arm 110 and lower arm 120.

Other arrangements for positioning actuator 150 with respect to upperarm 110 and lower arm 120 are also contemplated as being within thescope of the present invention. It is possible, for example, thatactuator 150 may be positioned below upper arm 110 and lower arm 120,with actuator 150 coupled to frame 130 and upper arm 110. It is alsopossible that actuator 150 may be positioned between upper arm 110 andlower 120, with actuator 150 coupled to frame 130 and upper arm 110and/or lower arm 120.

FIG. 5A shows one embodiment of a shackle 140 in accordance with thepresent invention. Shackle 140 is coupled to upper arm 110 and lower arm120 by second upper pin 142 and a second lower pin 144, respectively.Second upper pin 142 may have a cap or head 528 on one end, and a slot521 on the other end for receiving a fastener 520. First lower pin 144has a stop 522 on one end and a slot 524 on the other end. Second lowerpin 144 passes through a torsion spring 526, which includes an outer leg529 and an inner leg 530. Torsion spring 526 is coupled to second lowerpin 144 by a spring bracket 525 that mates with inner leg 530 and slot524, such that inner leg 530 is fixed in place to prevent torsion spring526 from freely rotating about second lower pin 144. Second lower pin144 is prevented from rotating by stop 531 on shackle 140 which is matedwith stop 522 on lower pin 144 with a fastener 540. Shackle 140 may alsoinclude a dock bumper 180 (FIGS. 5C and 5D).

FIG. 5B shows one embodiment of a platform support 170 in accordancewith the present invention. Platform support 170 is configured to becoupled to lower pin 144 of shackle 140, and is capable of rotatingabout lower pin 144. As platform 160 is unstowed, platform 160 rotatesabout lower pin 144 and a channel 172 in platform support 170 slidablyengages upper pin 142. When platform 160 is unstowed to a horizontalposition, upper pin 142 stops at the end of channel 172 and allowsplatform support 170 to hold platform 160 in a substantially levelposition. Channel 172 may be suitably configured to mate with cap orhead 528 of upper pin 142. Platform support 170 is thus supported fromabove by upper pin 142 when unstowed. This allows the bottom of platform160 when unstowed to be at substantially the same level as or lower thanthe bottom of shackle 140.

When lift 100 is in the lowered position, platform 160 is capable ofresting on or near the ground. When lift 100 is in the vehicle bed orloading dock level position, platform support 170 may have raised sides214 (FIGS. 6A-6D) which cooperate with extension plate 200 to provide aguide for loading and unloading on platform 160. When lift 100 is in thestowed position shown in FIG. 3A, the stowed platform 160 has a lowerprofile because it is coupled to lower pin 144. This lower profile mayreduce the required length of extension plate 200 needed to provideproper clearance to lift 100. When platform 160 is in the unstowedposition shown in FIGS. 3D-3E, outer leg 529 of torsion spring 526 arebiased against platform support 170 and help in stowing and unstowing ofplatform 160.

In other embodiments within the scope of the present invention, platformsupport 170 may include a tab or other structure in place of, or inaddition to channel 172 that stops against upper pin 142 when platform160 is unstowed Shackle 140 may also include one or more structures forcoupling of platform 160 and/or for engaging channel 172 or platform 160itself. Platform support 170 and platform 160 may thus be supported byupper pin 142 or any part of shackle 140. While not required, it ispreferred that platform 160 be supported from a location that is aboveor at substantially the same level as lower pin 144. Although shackle140, platform 160, and platform support 170 are shown as separateelements in the embodiments described, any combination of these threeelements may be formed as a single piece. In another embodiment, shackle140 may also be taller or longer than illustrated and support platform160 with a chain, cable or linkage attached between platform 160 andshackle 140, in addition to or in place of platform support 170.

FIGS. 5C-5D shows views of one embodiment of dock bumper 180, withextension plate 200 cut away to show detail. Dock bumper 180 may preventdamage to lift 100 when attached to a vehicle, for example, that isbacked into a dock or other structure. Extension plate 200 includes ahousing 202 to receive shackle 140, and shackle 140 is configured topress against the inside of housing 202 when lift 100 is in a stowedconfiguration, so as to transfer force from dock bumper 180 to extensionplate 200 and minimize or prevent damage to other parts of lift 100 suchas upper arm 110 and/or lower arm 120. Extension plate 200 in turn isconfigured to transfer force from shackle 140 to the vehicle. Mountingdock bumpers 180 on shackles 140 instead of extension plate 200 allowsextension plate 200 to be designed with a greater useful width.

As shown in FIGS. 5C-5D, the linkage system may also include an activeopener arm 125, which assists in the stowing and unstowing of platform160. Active opener arm 125 is coupled to upper arm 110 by an extension123. When lift 100 moves from a raised to a lowered position,translation of upper arm 110 and extension 123 causes active opener arm125 to rotate and exert pressure against platform 160, forcing platform160 outward towards its unstowed orientation. Likewise, when lift 100moves from a lowered to a raised position, active opener arm 125 iscaused to rotated in an opposite direction and lower platform 160resting thereon towards a stowed orientation. Further details regardingthe structure and function of such an active opener arm are described incopending U.S. application Ser. No. 10/789,909, the disclosure of whichis incorporated herein by reference.

FIGS. 6A-6B shows one embodiment of an extension plate 210 in accordancewith the present invention. Extension plate 210 includes a surface plate212 with hinged sections 214. Hinged sections 214 are capable of lyingflush with surface plate 212, as shown in FIG. 6A. FIG. 6B shows thatwhen platform 160 of lift 100 is raised, shackles 140 will raise hingedsections 214, which may then cooperate with the raised sides of platformsupport 170 to provide a guide for loading and unloading. When platform160 reaches the bed level position, platform 160 will be substantiallycoplanar with surface plate 212 and the vehicle bed or loading docksurface. When platform 160 is lowered, hinged sections 214 will dropback down.

FIGS. 6C-6D show another embodiment of an extension plate 220 inaccordance with the present invention that is configured to receivelocking rods (not shown) that are known in the art to be found onconventional side-swinging doors. In order to accommodate such lockingrods, extension plate 220 includes a surface plate 222 with a centersection 224. FIG. 6C shows center section 224 lying flush with surfaceplate 222. FIG. 6D shows center section 224 moved to allow locking rodsto be passed through extension plate 220. In the embodiment shown,center section 224 is hinged at the outboard edge of extension plate 220and swings outward. Center section 224 may have a latch 226 to help keepit closed. In other embodiments, center section 224 may be removable,slidable, spring-loaded, hinged at the inboard edge of extension plate220 and swing inward, or configured with any other suitable mechanism toprovide clearance to locking rods. In yet another embodiment, surfaceplate 222 includes arcuate grooves or channels which provide clearancefor the locking rods.

As seen in FIGS. 6C-6D, extension plate 220 also includes permanentlyraised sections 216, rather than the hinged sections 214 associated withextension plate 210. It is within the scope of the present inventionthat hinged sections 214 may be included in extension plate 220, andcenter section 224 which accommodates locking rods may also be used withthe extension plate 210 shown in FIGS. 6A-6B.

FIGS. 7A-7B show one embodiment of an underride 190 in accordance withthe present invention. Underride 190 acts as a rear impact guard andprevents other vehicles from traveling underneath lift 100. Underride190 includes an underride bar 191 which may be coupled to frame 130 byplates 192. Plates 192 may be coupled to frame 130 at the same point aslower arms 120. This transfers most or all of any impact force tounderside 190 to frame 130 and not to lower arms 120. Plates 192 mayinclude adjustment holes 194 which couple to lower arms 120 and allowunderride 190 to be adjusted to a desired height. Underride 190 may alsoact as a synchronizing or balancing structure which minimizes binding or“walking” of upper arm 110 and lower arm 120 on each side of lift 100 asit is being operated.

FIGS. 8A-8B shows how a lift 100 according to the present invention maybe shipped as a package with extension plate 200 and then installed on avehicle. In this manner, lift 100 and extension plate 200 may comepre-adjusted from the factory. Extension plate 200 may be held in theproper position with respect to the rest of lift 100 by a tack-weld 310(FIG. 8B), an installation bracket 320 (FIG. 8A), or any other suitablefastener or removable coupling. To install lift 100 and extension plate200, extension plate 200 is leveled before being welded or otherwisecoupled to the vehicle, and then lift 100 is welded or otherwise coupledto the vehicle. After tack-weld 310 is cut and installation bracket 320is removed, lift 100 has been properly installed. The installation oflift 100 and extension plate 200 are facilitated by the fact that lift100 and extension plate 200 are shipped pre-adjusted, lift 100 andextension plate 200 do not need to be disassembled before installation,and once extension plate 200 has been properly coupled to the vehicle nofurther adjustment of lift 100 will typically be necessary before lift100 can be coupled to the vehicle.

While the invention has been described in terms of some specificexamples and in some specific embodiments, it will be clear that thisinvention is not limited to these specific examples and embodiments andthat many changes and modified embodiments will be obvious to thoseskilled in the art without departing from the true spirit and scope ofthe invention as defined in the appended claims. The scope of theinvention is, therefore, indicated by the appended claims rather thanthe foregoing description. All changes which come within the meaning andrange of equivalency of the claims are to be embraced within theirscope.

1. A liftgate assembly comprising: a mount assembly that is mountable toan associated vehicle, the mount assembly comprising at least one framemember; a platform having first and second ends; a lift assembly thatraises and lowers the platform, the lift assembly comprising a supportarm having a first end operatively attached to the frame member and asecond end operatively attached to the platform; and a bed extensioncomprising: (a) a first side that abuts the associated vehicle; (b) asecond side that abuts the first end of the platform only when theplatform is in a raised position; (c) a traffic surface that receivedtraffic for loading and unloading cargo; (d) a first opening; and (e) afirst cover movable when contacted by the support arm from a firstposition covering the first opening to a second position where thesupport arm extends through the first opening.
 2. The liftgate assemblyof claim 1 wherein when in the first position, no portion of the firstcovet extends above a plane defined by the traffic surface of the bedextension.
 3. The liftgate assembly of claim 1 wherein when in thesecond position, a portion of the first cover extends above a plandefined by traffic surface of the bed extension.
 4. The liftgateassembly of claim 1, wherein the first cover is pivotally connected tothe bed extension.
 5. The liftgate assembly of claim 1, wherein thefirst end of the support arm is pivotally attached to the frame memberand the second end of the support arm is pivotally attached to theplatform.
 6. The liftgate assembly of claim 1, wherein: the second sideof the bed extension has a first gap partially defining the firstopening; and, the first cover has a first end that substantially coversthe first gap when the first cover is in the first position.
 7. Theliftgate assembly of claim 1, wherein the lift assembly also moves theplatform into a folded position.
 8. The liftgate assembly of claim 7,wherein the lift assembly further comprises: at least one cylinder thatmoves the platform between the folded position, a raised position and alowered position.
 9. A liftgate assembly comprising: a mount assemblythat is mountable to an associated vehicle, the mount assemblycomprising at least one frame member; a platform having first and secondsides and first and second ends; a lift assembly that raises and lowersthe platform, the lift assembly comprising: (a) a first support armhaving a first end pivotally attached to the mount assembly and a secondend pivotally attached to the first side of the platform; and (b) asecond support arm having a first send pivotally attached to the mountassembly and a second end pivotally attached to the second side of theplatform; and a bed extension comprising: (a) a first side that abutsthe associated vehicle; (b) a second side that abuts the first end ofthe platform only when the platform is in a raised position; (c) atraffic surface that receives traffic for loading and unloading cargo;(d) a first opening; (e) a first cover movable when contacted by a thefirst support arm as the platform is being raise from a first positioncovering the first opening to a second position where the first armextends through the first opening; (f) a second opening; and (g) asecond cover movable when contacted by the second support arm as theplatform is being raise from a first position covering the secondopening to a second position when the second support arm extends throughthe second opening.
 10. The liftgate assembly of claim 9, wherein thefirst and second covers are pivotally connected to the bed extension.11. The liftgate assembly of claim 9, wherein the lift assembly alsomoves the platform into a folded position.
 12. The liftgate assembly ofclaim 9, wherein the lift assembly further comprises: at least onecylinder that moves the platform between the folded position, a raisedposition, and a lowered position.